Three back-to-back storms expected to soak the region through Sunday

It's not a perfect storm but a series of back-to-back deluges, possibly starting with a lightning-and-thunder show, assembled to soak the thirsty hills of the Bay Area starting Wednesday morning.

The first blow of the triple whammy was predicted to hit the South Bay sometime "between sunrise and the morning commute Wednesday," said forecaster Bob Benjamin of the National Weather Service. While the brunt is expected to move through farther north, Benjamin said the Santa Clara Valley can expect between a half-inch and an inch of rain, and at least two inches expected on the coastal mountains.

While that's nothing to sneeze at, the South Bay will then say hello to the storm's stronger siblings.

With barely a break between them, the second wet guest is expected late Thursday or early Friday, and the last blast should hit Sunday morning, Benjamin said. He called those storms "more ominous," each dumping an inch or two in San Jose, while the Peninsula will be a mixed bag, with the coastside taking the brunt of rainfall as the mountains squeeze out the juice.

And there will be wind -- gale warnings over coastal waters, and gusts reaching 50 mph in the mountains and coast. In the valley, there's a "shadow effect" due to the surrounding mountains but it could still blow 35 to 40 mph, he said.

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Jan Null, a meteorologist with Golden Gate Weather Services in Saratoga, said meteorologists call what's going on an "atmospheric river" -- conditions conducive to letting storms move into the area, one after the other. He said that's common, but this system is unusual in where it hails from.

"The media jargon is 'pineapple express,'" he said. "It is tapping into subtropical moistures, coming in from the southwest roughly in the direction of Hawaii. You can have greater rain potentials, and higher snow levels."

Storm temperatures are expected to range from the low 50s to the low 60s throughout the Bay Area, Benjamin said.

For water officials, the storms mean the possibility that this season's lower-than-average rainfall could get bumped up to speed. As of Tuesday evening, San Jose rainfall totals were 55 percent of normal, while Santa Clara County reservoirs were at 35 percent of capacity.

"It's always a double-edged sword," said Marty Grimes, spokesman for the Santa Clara Valley Water District. "We absolutely need the water, but for it to all come down at once can cause problems."

Those problems include ponding on roadways and small stream flooding, Benjamin said, and also power outages, downed trees and landslides for people who live in prone areas. "They know who they are," he said.

Grimes said water district crews have been doing prep work, clearing 57,000 cubic yards of sediment out of creeks since summer. They've made a circuit of local waterways looking for blockages as a pre-emptive strike against flooding, and set up webcams to monitor three notorious problem spots -- the El Camino storm drain in Sunnyvale, and trash racks in West Little Llagas and Almendra creeks in Morgan Hill and Los Gatos.

He said residents can help a lot by checking on the storm drains near their home.

"They're real susceptible, especially with all the leaves falling," he said. "They get clogged with the leaves, branches and debris, and that's when you're going to get street flooding."

Null said that while the early system is beneficial, it doesn't portend how wet the season will get.

"We can have one big November and then it stops," he said. "There's no good indicator of what the rest of winter will bring."